The use of computers and computerized methods to provide drawings and designs is becoming more and more common.
A goal of computer-aided design (CAD) is to provide a designer with the capability to describe a design, analyze a drawing for a design, modify the design, and store copies of the drawings at all phases of the development process. Progress in CAD systems and methods, in some sense, can be measured by the flexibility offered to the designer and the complexity of the design and drawing that is possible.
The typical CAD approach calls for the user or designer to specify a geometric element such as a point, line or circle, and then to specify the size features of the element where applicable. By way of example, the user or designer might specify a circle, locate the center of the circle by positioning a cursor at the center, and then specify the size by moving the cursor a distance from the center equal to the desired radius for the circle. The system would then execute a drawing for such a circle and display it to the user. The information in the system and the display then reflects a precise circle (within the limits and tolerances of the system). Other precise geometry, then, can be added to the drawing using similar or analogous operations.
This approach, including the interaction with the user, of course is not in accordance with the natural way that human beings create drawings. That natural way involves the movement of a drawing implement by the user's hand. Further, many designers are most creative in "sketching out" drawings lacking in the standards applicable to formal drawings for a design.
The device sold by Apple Computer Inc. under the name Newton provides some sketching capabilities, perhaps best described as a "notebook" capability in a non-CAD environment. It is adapted to create more precise-looking, single-element paths, such as circles and ellipses, and more precise-looking, multi-element paths, such as a series of straight lines, from sketching by a user. It is also adapted to incorporate and impose concomitant geometric constraints, such as coincident end points for adjacent line elements.
The present invention provides sketching-type drawing capabilities consistent with and incorporated into a CAD environment. This includes a variety of geometrical constraints between drawing parts and elements which are of significance in a CAD environment. The geometrical drawing parts or elements include points, straight lines, open arcs, circles and ellipses.
With the capability to interpret a sketched indicator path as any one of these, there is also the capability to distinguish and recognize, delete and "areafill" symbols.
It also provides the capability to distinguish and interpret relatively complex multiple-element strokes. It does this by determining break locations for the elements along the stroke, and recognizing these elements before re-constituting a stroke meeting standards for precision.